class %SYNC.SyncSet extends %Library.RegisteredObjectCaché Objects provides a toolkit for synchronizing objects of selected types between namespaces containing compatible type classes. The core of the synchronization toolkit is the SyncSet. A SyncSet contains all of the objects of selected types that have been filed in the local database from a defined starting time up to an ending time. "Time" in the context of synchronization means a sequencing value and is not an "hours-minutes-seconds" value. Object Synchronization consists of three primary tasks. The first task is to build the SyncSet. That task involves determining which objects are to included in the SyncSet. Caché uses a transaction journal for that purpose. The transaction journal is implemented as %Library.ObjectJournalTransaction. Any persistent or serial class that declares the class parameter OBJJOURNAL as true will record all filing events in %Library.ObjectJournalTransaction. The second task is to add changed objects to the SyncSet. The most common mechanism for performing this task is to retrieve the object state from the system journal using information recorded in %Library.ObjectJournalTransaction. This mechanism allows historical object data to be included in the SyncSet. If the system journal is not available, there is a provision to include the current object state. The third task is to import the SyncSet into the namespace being synchronized. This involves loading the SyncSet global into the target namespace and then importing each object contained in the SyncSet. If an object being imported already exists in the target namespace then the timestamp for the imported object is compared to the timestamp of the existing object. If a conflict is detected then user implemented code is called to resolve the conflict. This is essentially an optimistic concurrency mechanism. If the conflict is not resolved successfully then a concurrency error is reported and the object is not synchronized.
This is a string value used to identify the Sync Set object. This value is used as the suffix to the global name root of ^OBJ.SYNC.. For example, if the sId is set to the integer 1 then the global name will be ^OBJ.SYNC.1.
This method synchronizes each object contained in the sync set with the current database. Each object is first checked for concurrency. Concurrency conflicts occur when the object is modified on the local system after the object was last synchronized with the remote system where the sync set originated. If a concurrency conflict is detected, the object is passed to the %ResolveConcurrencyConflict method in %Library.SwizzleObject. If the conflict cannot be resolved, the object is requeued for later processing and the concurrency error is reported in the %%SERR error log. Otherwise, the object is synchronized by passing it to the %SyncObjectIn method in %Library.SwizzleObject.. If the synchronization fails, then the object is requeued for later processing.
There are two types of common synchronization errors. The first is an unresolved dependency. This type of error occurs when an object references another object and the referencing property is part of a REQUIRED constraint. That means the object cannot be saved until the reference can be resolved. This problem is often caused by a reference to an object that is in the sync set but has not yet been processed. The second type of problem is an unresolved reference. This type of problem occurs in the same was as an unresolved dependency but the reference is not required in order for the object to be saved. An object with an unresolved reference is partially synchronized and only the reference is requeued for later processing.
Once all of the objects in the sync set have been processed, the Import method attempts to synchronize all objects that were requeued. During this phase, all of the unresolved dependencies and references are expected to be resolved. Any objects that fail to synchronize during this phase are left in an unresolved state. Unresolved objects and errors reported during synchronization can be accessed by using the Unresolved query or the Errors query.
When all of the objects contained in the Sync Set have been processed the time stamps in the %SYNC.SyncTime class are updated using the maxTS value.
|file||The name of a file containing a sync set. If a file name is specified, then that file will be loaded into the global. If no file is specified, then the global is expected to already exist in the current namespace.|
An integer value indicating the SyncTime value when this System.Namespace was last synchronized with the System.Namespace that generated the sync set being imported. If this value is not specified, then it will be retrieved from %SYNC.SyncTime
The highest transaction ID contained in the sync set. It is used to set the rTrn property in the %SYNC.SyncTime class. This value is not used for any purpose during import and is maintained for informational purposes only. This value is specified by the user and is expected to be the ID of the last %Library.ObjectJournal object included in the sync set. See the %SYNC.SyncTime for more information on the rTrn and lTrn properties.
Option flags. This formal argument is maintained for backward compatibility only.
Array of errors encountered during import. These are not errors encountered during synchronization but are errors reported doing tasks like opening the file.
If true, then Import will display status information on the current device.
If true, then Import will record all import activity in the sync set global under the "Trace" subscript.